Emitter wire with layered cross-section

Abstract

By selecting different materials for each layer, a multi-layered electrode structure can be made with superior performance characteristics. For example, a multilayered electrode can include a high tensile strength tungsten core, a conductive intermediate palladium, palladium-nickel, or other platinum group metal layer for generating a corona discharge, and a hardened layer comprising rhodium or other platinum group metal or alloy of the same to resist frictional abrasion during removal of silica dendrites that accumulate on the electrode surface during operation.

1 . A multi-layered electrode for use in an electrohydrodynamic device, the electrode comprising:
 an elongated electrode core material;   one or more intermediate conductive layers each comprising a platinum group metal disposed about the electrode core material; and   a further electrode layer comprising rhodium over the one or more intermediate conductive layers.   
     
     
         2 . The electrode of  claim 1 , wherein the further layer presents a hard rhodium surface substantially resistant to abrasion during repeated frictional removal of silica dendrites that accumulate thereon during operation of the electrohydrodynamic device. 
     
     
         3 . The electrode of  claim 1 , wherein the one or more intermediate conductive layers includes at least a first intermediate layer comprising substantially pure palladium and a second intermediate layer comprising an alloy of palladium and nickel. 
     
     
         4 . The electrode of  claim 1 , wherein the one or more intermediate conductive layers includes first and second intermediate layers of two different alloys of palladium and nickel, with a harder one of the two alloys positioned over a softer one of the two alloys. 
     
     
         5 . The electrode of  claim 1 , further comprising a sacrificial conditioning material comprising silver deposited over the further electrode layer. 
     
     
         6 . The electrode of  claim 1 , wherein a first of the one or more intermediate conductive layers comprises a substantially pure palladium coating over the electrode core, a second intermediate conductive layer comprises a first palladium nickel alloy coating over the substantially pure palladium coating and a third intermediate conductive layer comprises a second palladium nickel alloy coating over the first palladium alloy coating, wherein the second palladium alloy coating is harder than the first palladium nickel alloy coating. 
     
     
         7 . The electrode of  claim 6 , wherein each successive intermediate conductive layer is increasingly durable to at least partially mitigate exposure of underlying materials to a corona discharge environment following at least one of micro-crack formation, pinhole formation, defect formation, erosion and consumption of a portion of a successive layer. 
     
     
         8 . The electrode of  claim 6 , wherein the second palladium nickel alloy coating is selected to mitigate at least one of abrasion and erosion of a softer first palladium nickel alloy coating in the event of compromise of a portion of the further layer comprising rhodium and of a silver layer over the further layer. 
     
     
         9 . A multi-layered electrode for use in an electrohydrodynamic device, the electrode comprising:
 an elongated electrode core material;   a first conductive layer comprising a platinum group metal over the electrode core material; and   at least a second conductive layer comprising an alloy of a platinum group metal over the electrode core material, wherein the composition of the second conductive layer differs from the composition of the first conductive layer.   
     
     
         10 . The electrode of  claim 9 , further comprising a further electrode layer comprising rhodium over the second conductive layer. 
     
     
         11 . The electrode of  claim 9 , wherein the first conductive layer comprises substantially pure palladium and the second conductive layer comprises a palladium-nickel alloy. 
     
     
         12 . The electrode of  claim 9 , wherein the electrode core material comprises at least one of tungsten, titanium, steel, tantalum, molybdenum, nickel, and an alloy comprising one of tungsten, titanium, steel, tantalum, molybdenum, and nickel. 
     
     
         13 . The electrode of  claim 9 , wherein the electrode core material comprises tungsten and rhenium. 
     
     
         14 . A method of forming an electrode, the method comprising:
 providing an electrode core material;   providing a first intermediate conductive layer comprising a platinum group metal over the electrode core material; and   providing a second intermediate electrode layer over the first intermediate conductive layer, the second intermediate electrode layer comprising a different alloy of a platinum group metal than the first intermediate conductive layer.   
     
     
         15 . The method of  claim 14 , wherein the first intermediate conductive layer material comprises at least one of palladium and an alloy of palladium and nickel. 
     
     
         16 . The method of  claim 14 , further comprising providing a further conductive layer comprising rhodium over the second intermediate electrode layer. 
     
     
         17 . The method of  claim 16 , further comprising depositing a conditioning material comprising silver along at least a portion of a length of the electrode. 
     
     
         18 . An electrohydrodynamic device (EHD) comprising:
 one or more collector electrodes; and   a layered emitter electrode in spaced relation to the one or more collector electrodes; the layered emitter electrode and one or more collector electrodes being energizable to motivate fluid flow along a flow path;   wherein the layered emitter electrode comprises:
 an electrode core material; 
 two or more intermediate conductive layers about the core material, the two or more intermediate conductive layers each comprising a platinum group metal, the first intermediate conductive layer being of a different composition than a second of the intermediate conductive layers; and 
 a further electrode layer comprising rhodium and presenting a hard surface to resist abrasion during repeated frictional removal of silica dendrite accumulated thereon from operation of the EHD. 
   
     
     
         19 . The device of  claim 18 , wherein the first intermediate conductive layer comprises palladium and the second intermediate conductive layer comprises a palladium-nickel alloy. 
     
     
         20 . The device of  claim 18 , further comprising a sacrificial silver coating over the further electrode layer. 
     
     
         21 . An apparatus comprising:
 an enclosure; and   a thermal management assembly for use in convection cooling of one or more devices within the enclosure, the thermal management assembly defining a flow path for conveyance of air between portions of the enclosure over heat transfer surfaces positioned along the flow path to dissipate heat generated by the one or more devices, the thermal management assembly including an electrohydrodynamic (EHD) fluid accelerator comprising:   one or more collector electrodes; and   a layered emitter electrode in spaced relation to the one or more collector electrodes; the layered emitter electrode and one or more collector electrodes being energizable to motivate fluid flow along a flow path;   wherein the layered emitter electrode comprises:
 an electrode core material; 
 one or more intermediate conductive layers about the core material, the one or more intermediate conductive layers each comprising a platinum group metal; and 
 a further electrode layer comprising a platinum group metal and being of a different composition than the one or more intermediate conductive layers; 
 wherein the composition of one or more of the intermediate conductive layers is configured to mitigate intralayer propagation of microcracks formed in the further electrode layer. 
   
     
     
         22 . The apparatus of  claim 21 , wherein the one or more devices includes one of a computing device, laptop computer, tablet computer, smart phone, projector, copy machine, fax machine, printer, radio, audio or video recording device, audio or video playback device, communications device, charging device, power inverter, light source, medical device, home appliance, heater, air cleaner, power tool, toy, game console, set-top console television, and video display device.